This invention relates to a mutiprocessor ATM exchange and more particularly to a method for implementing SVC (switched virtual channel) by use of B-ISUP (broadband ISDN (integrated services digital network) user part).
Conventionally, to implement SVC in a multiprocessor exchange, when a plurality of call control processors is allocated to one node, a logic (call's floating) is required to determine which call control processor should be used to process signals for controlling calls.
The ISDN user part (ISUP) is used as a call control protocol in a toll switch of a narrow-band exchange system. In this case, a circuit (line) number is set in a call control signal and floating is implemented by associating the line number with a call control processor.
The above mentioned floating will now be explained with reference to FIG. 7. In this case, the number system of circuits in a local node is temporarily named comn and a circuit number common to an adjacent exchange is cic.
In conventional exchange nodes, cic understandable to both exchange nodes opposite each other is set in signals received by a common signaling processor to represent a circuit number.
Accordingly, a cic-to-comn conversion table and a comn-to-CLP (call control processor) number conversion table are prepared in advance in exchange nodes. When a call control signal is received, the CLP number of a call control processor is determined from cic by referencing these tables and floating can be implemented.
For example, as shown in FIG. 7, when a circuit number is cic#i, the number system of circuit is comn#j, the clp number "CLPno#k" of a call control processor is set to take correspondence with the number system comn#j of the channel line, cic#i is converted to comn#j by the cic-to-comn conversion table (see (a) in FIG. 7) and comn#j is converted to CLPno#k by the comn-to-clp number conversion table (see (b) in FIG. 7). Thus, CLPno#k is determined from cic#i.
In the above mentioned ISDN exchange node, as shown in FIG. 6, an initial address message (IAM) and an address complete message (ACM) are relayed. In FIG. 6, ISUP protocol processing is included in the incoming call control and the outgoing call control.
Namely, on receiving an IAM from a preceding exchange (an exchange relaying the initial address message), a common signaling processor (CSP) extracts the circuit number (cic) of the incoming circuit from the signal, references the above mentioned conversion tables to perform cic-to-comn conversion and comn-to-clp number conversion, and determines an incoming side clp number (e.g., #1) (step S21 in FIG. 6).
Accordingly, the common signaling processor performs floating the IAM to the input call control of the determined call control processor (CLP) of the clp number (#1). The call control processor of the clp number (#1) acquires the internal call reference number and starts call state management (step S22 in FIG. 6).
The call control processor of the clp number (#1) links the number system (comn) of circuit line with an internal call reference number (step S23 in FIG. 6) and determines a call transfer destination by analyzing the digits of the incoming number (step S24 in FIG. 6). Subsequently, the call control processor of clp number (#1) selects a route to the destination (step S25 in FIG. 6), selects the circuit number (cic) of outgoing circuit (step S26 in FIG. 6), references the above mentioned conversion tables to perform cic-to-comn conversion and comn-to-clp number conversion, determines an outgoing side clp number (e.g., #2), and holds the outgoing side clp number (step S27 in FIG. 6).
The call control processor of clp number (#1) transfers the incoming internal call reference number to the outgoing call control of a call control processor of clp number (#2). The call control processor of clp number (#2) acquires the internal call reference number, starts call state management, and holds the incoming call control clp number and internal call reference number (step S28 in FIG. 6). At this time, since the call control processor of clp number (#2) transfers an output internal call reference number to the incoming call control of the call control processor, the call control processor of clp number (#1) holds the outgoing internal call reference number (step S29 in FIG. 6).
Subsequently, the call control processor of clp number (#2) links the number system of channel line with the internal call reference number (step S30 in FIG. 6). In response to this, the common signaling processor (#2) sends an IAM to a succeeding exchange (an exchange to relay an IAM received by the local exchange to).
On receiving an address complete message from the succeeding exchange in response to the sent IAM, the common signaling processor (2#) extracts the circuit number (cic) of outgoing circuit from the address complete message, references the above mentioned conversion tables to perform cic-to-comn conversion and comn-to-clp number conversion, and determines an outgoing clp number (#2 in this case) (step S31 in FIG. 6).
According to the determination of the common signaling processor (#2), the call control processor of clp number (#2) extracts an internal call reference number from the number system (comn) of outgoing circuit and changes call state corresponding to the internal call reference number (step S32 in FIG. 6). Subsequently, the call control processor of clp number (#2) extracts the held incoming call control clp number (#1) and internal call reference number (step S33 in FIG. 6), and transfers the incoming internal call reference number to the incoming call control of the call control processor of the clp number (#1).
The call control processor of the clp number (#1) changes call state (step S34 in FIG. 6). On receiving notification of call state change in the incoming call control of the call control processor of the clp number (#1), the common signaling processor (#1) sends an address complete message to the preceding exchange,
If B-ISUP is used to implement SVC with the above mentioned multiprocessor exchange, since single node selection of resources (speech channel) is made in B-ISUP, no speech channel may not be determined as a result of routing, so that speech channel information may not be set in an IAM.
Accordingly, when an ATM (asynchronous transfer mode) exchange using the call control signal protocol B-ISUP of broadband system is configured with above mentioned conventional multiple processors, the floating logic used in the call control signal protocol ISUP of narrow band system cannot be applied.
One side selection of resources will now be described. As shown in FIG. 8, for example, the following describes the case where adjacent nodes assigned point codes 20 (PC #20) and 10 (PC #10) respectively and resources VP #1, #2, #3, #4 and #5 exist between the nodes.
According to one side selection of resources, in the case described above, when a node (PC #20) having greater point code has the right to select resources (VP #2 and VP #4) of even numbers and a node (PC #10) having smaller point code has the right to select resources (VP #1, VP #3, and VP #5) of odd numbers, one node is informed which resources acquired by another node having selection right. In this case, resource acquisition is completely separated and collision will not occur between the nodes. In FIG. 8, the circle (.largecircle.) denotes selection right.